Many different signaling molecules can induce cell migration by activating the small GTPase Ras, which in turn activates both phosphatidylinositol 3-kinase (PI3K) and extracellular signal-regulated kinase (ERK) pathways. The PI3K pathway stim- ulates actin polymerization and the forma- tion of a lamellipodial protrusion at the leading edge of the cell, but how ERK sig- naling promotes cell motility is less well understood. Tanimura et al. now reveal that one function of the ERK pathway is to inactivate a negative regulator of the myo- sin MyolE, allowing the motor protein to move to the tips of lamellipodia where it can facilitate cell movement (1).
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